Modern elevator systems utilize sophisticated software and controllers which control most aspects of an elevator's operation. The controllers gather information from various sources in the elevator system and use such information to efficiently operate the elevator. Thus, elevator speed, elevator creep period, starting, stopping, floor positioning or leveling, and the like are all governed by the controller. Each of these functions are affected by variations in floor distances, friction, and stiction. Many older buildings, for example, have large variations in the distance between each landing. Additionally, friction and stiction varies from one elevator system to another, and also within each elevator system.
In a closed loop elevator system, the elevator functions mentioned above are generally monitored by using an encoder which measures motor shaft revolutions and translates the results into machine readable feedback signals delivered to the controller microprocessor. The controller uses these feedback signals to determine the present status of the elevator functions. If a deviation from a desired result is detected, then the controller attempts to provide appropriate compensation. For example, conventional elevator systems determine the time to begin deceleration during an elevator run by using the feedback signals supplied by the encoder. The encoder, however, introduces added expense and complexity into the elevator system. Accordingly, it is desirable to perform the above mentioned functions without the use of an encoder.